The behavioral correlates of activity in reticular formation (RF) neurons have not been systematically studied in unrestrained animals. Using a recently developed microwire recording technique that permits single unit recording in the unrestrained, freely moving cat, we have discovered that neurons in the RF discharge in relation to specific movements. Cells whose discharge related to head, paw, tongue, ear, scapula or facial movements have been identified. We propose the following hypothesis: that discharge in most RF cells is primarily related to the excitation of specific muscle groups. We show how this hypothesis can reconcile many of the contradictory conclusions that have been reached about the functional relations of these neurons. The proposed research seeks to test this hypothesis while systematically studying and mapping the behavioral correlates of midbrain, pontine and medullary RF units. 1) Visual and polygraphic observations will be employed to determine the motor relations of rabbits during spontaneous movements and during systematic behavioral manipulation. Reinforcement of increased rates of unit discharge will be used to clarify relationships between RF activity and behavior. Cells will be studied after blocking the cats' muscle activity with Flaxedil, in order to determine if proprioceptive input is required for RF activation. Units will be monitored during sleep-waking cycles to determine if any group of RF cells discharges selectively in REM sleep and could therefore have an "executive" role in its control. 2) Photographic techniques will be used to describe the temporal relationship between unit discharge and movement, and determine the precise topography of movements related to unit activity. The tegmental lesion preparation will be used to ascertain if PRF unit activity related to REM sleep movements in the same way that it relates to waking movements. 3) Spike triggered averages of EMG activity will be used to determine if the different classes of RF units are synaptically related to activity in recorded sites, and to investigate the pattern of unit-muscle relationships. Thus, this research will be apt to answer basic behavioral questions about these cells (i.e., what are their discharge correlates) as well as fundamental neurophysiological questions (i.e., what are their synaptic actions).